The first artificial mitral valve was implanted in children at this institute over 25 years ago. Annual examinations at the NHLBI Surgery Clinic over a period of 15 to 20 years has permitted description of a unique patient population of children who have now entered adulthood in their second decade of artificial valve function. All surviving children (N=6) with mitral valve prosthesis in place for at least 15 years, were reevaluated at the NHLBI Surgery Branch clinic. The presence of previous multiple cerebral infarctions was found by computerized axial tomography in three patients who had exhibited no clinical history suggestive of central thromboembolism and all four patients with a mechanical prosthesis. A complete neurological examination failed to demonstrate any residua of these multiple cerebrovascular accidents in all patients. A consistent discrepancy between the history of exercise tolerance elicited from the patient interview and objective data from the tread mill exercise capacity was also demonstrated. Echocardiogram confirmed tread mill evidence for reduced left ventricular function in these long term survivors. No kidney scan was positive for emboli. We conclude that the frequent presence of subclinical central thromboemboli and the inability of patient history to confirm exercise capacity in these young adults mandates the use of more objective modalities in the long term follow up of prosthetic valve complications in children.